Ground-based active sensors have been used in the past with success at detecting nitrogen (N) variability within maize production systems. The use of unmanned aerial vehicles (UAVs) presents a new opportunity to evaluate N variability with unique advantages compared to ground based systems. Two datasets were used to quantify the appropriate operating distance above a crop canopy, and make comparisons between ground-based systems and a UAV-mounted active sensor. In this study, an active sensor mounted on a UAV was able to detect differences similarly to the handheldbased sensor. Distance from canopy sensing capabilities are sensor-specific, which needs to be taken into account when implementing such a system. The Aerial Active platform used in this study was shown to operate effectively within a range of 0.5 to 1.5 m above the canopy. Unmanned aerial vehicles provide potential for automated data collection to quantify crop stress using active sensors.